In recent years, there are applied in various field methods of preparing precise conductive films, ceramic films and glass films by coating paste obtainable by dispersing inorganic powder such as conductive powder, ceramic powder and glass powder in a binder resin and then burning the coated paste after a debinder step.
Laminate type electronic devices such as a laminated ceramic condenser are generally produced by following the steps as follows (for example, as described in Patent Document No. 1 and Patent Document No. 2).
First, to a solution obtainable by dissolving a binder resin such as a polyvinyl butyral resin and a poly(meth)acrylic ester resin in an organic solvent, a plasticizer and a dispersant are added, and then to this, ceramic raw material powder was added and the resulting mixture is mixed homogeneously with a ball mill and the like and defoamed to obtain a ceramic slurry composition having a certain viscosity. The obtained slurry composition is applied by casting onto the surface of a supporting member such as a polyethylene terephthalate film or SUS plate subjected to releasing treatment using a doctor blade, a reverse roll coater, etc. The applied slurry composition is heated to evaporate volatile components such as the solvent, and then a dried slurry composition is peeled off from the supporting member to obtain a ceramic green sheet.
Next, a plurality of processed sheets, which is formed by applying conductive paste formed by dispersing metal powder such as palladium and nickel in a binder resin and a solvent onto the obtained ceramic green sheet by screen printing and the like, are alternately overlaid, and the respective layers of this overlaid substance are thermally attached to another by pressure to obtain a laminate. After performing the treatment in which binder components contained in this laminate are removed by thermal decomposition, so-called degreasing treatment, the laminate was burnt out, and the resulting ceramic burnt body goes through the step of burning an external electrode on the end face of the resulting ceramic burnt body to obtain a laminated ceramic condenser.
And, in the case where laminated ceramic condensers are produced by such a method, when a ceramic green sheet coated with conductive paste is laminated, a level difference is generated between areas coated with conductive paste and areas not coated with conductive paste. In recent years, laminated ceramic condensers are required to have higher capacity and it is studied to further increase the number of layers and to reduce a film thickness. In the laminated ceramic condensers in which the number of layers is extremely increased and a film thickness is extremely reduced like this, there is a tendency that the level difference due to the presence or absence of coating the conductive paste is accumulated, and this causes peeling (delamination) between the ceramic green sheet and a conductive layer in pressing the laminate or deformation of a dielectric layer or a conductive layer at the end of the laminated ceramic condenser.
On the other hand, in Patent Document No. 3, there is described a method of preventing the occurrence of level difference by screen printing the conductive paste on the ceramic green sheet and then applying ceramic paste to an area on the ceramic green sheet, to which the conductive paste was not applied, by a method such as screen printing.
And, for example when plasma display panels are produced, they are generally produced by following the steps as follows. First, a display electrode and a bus electrode are formed on a glass substrate. By further forming a dielectric layer and a MgO layer on the glass substrate, a front glass substrate is prepared. On the other hand, by forming a data electrode, forming a dielectric layer and further forming barrier ribs and a fluorescent material layer on a glass substrate, a back glass substrate is prepared. These front glass substrate and back glass substrate are stuck to each other, air is exhausted, a discharge gas is filled and then a printed circuit board is implemented to complete the plasma display panel.
The barrier ribs are formed as follows in the steps of producing the back glass substrate (for example, as described in Patent Document No. 4 and Patent Document No. 5). A barrier rib material is applied to a glass substrate and a dry film resist is laminated. This laminated substrate is exposed through a photomask and developed to form a pattern. Then, the barrier rib material is cut in pattern form by sandblasting, and after a residual dry film resist is peeled, a pattern is subjected to burning. In this time, as a barrier rib material, there is used glass paste formed by dispersing a glass powder in a binder resin and a solvent.
As a binder resin for supporting such inorganic powders such as conductive powder, ceramic powder and glass powder, conventionally, ethyl cellulose resins have been mainly employed. Paste, in which ethyl cellulose is used as a binder resin, is superior in a coating property, and since particularly a coating method such as screen printing can be employed, coats having a precise form can be easily formed. However, ethyl cellulose had several significant problems.
For example, when ethyl cellulose is employed as a binder resin of conductive paste or ceramic paste for producing a laminated ceramic condenser, since it has low adhesive property to a ceramic green sheet in which a polyvinyl acetal resin is used as a binder resin, peeling between layers, so-called delamination, tends to occur. Particularly, in recent years, laminated ceramic condensers are required to have higher capacity and it is studied to further increase the number of layers and to reduce a film thickness, and therefore, the occurrence of delamination is critical in the laminated ceramic condensers in which a film thickness is extremely reduced like this. And, since ethyl cellulose has a poor thermal decomposition property, there was also a problem that a carbon component remains after burning even though it is subjected to degreasing treatment and therefore electric characteristics were impaired.
On the other hand, for example, when ethyl cellulose is used as a binder resin of glass paste for producing barrier ribs of a plasma display panel, there was a problem that since ethyl cellulose has low alkali resistance and low adhesive property to glass, peeling occurs in a developing step and the barrier ribs are not formed into a desired pattern.
For this situation, it is studied that a polyvinyl acetal resin is used as a binder resin for coating paste. Since a polyvinyl acetal resin has high adhesive property to a ceramic green sheet, it is thought that if it is used as a binder resin of conductive paste or ceramic paste for producing a laminated ceramic condenser, the problem of peeling between layers will be resolved. And, since the polyvinyl acetal resin has high alkali resistance, it is possible to inhibit the occurrence of peeling in a developing step when the polyvinyl acetal resin is used as a binder resin of glass paste for producing barrier ribs of a plasma display panel.
However, the paste obtained by using the polyvinyl acetal resin as a binder resin has a problem that it has a poor coating property and it causes problems such as being stringy and clogging particularly on the occasion of coating by screen printing and consequently a peel-off, property is deteriorated and the precision of thickness is reduced, and therefore patterns cannot be clearly drawn and production yields decrease.    Patent Document No. 1: Patent Kohyo Publication Hei-3-35762    Patent Document No. 2: Patent Kohyo Publication Hei-4-49766    Patent Document No. 3: Patent Kokai Publication 2002-280250    Patent Document No. 4: Patent Kokai Publication Hei-8-222135    Patent Document No. 5: Patent Kokai Publication 2002-63849